Rationale: The overall goal of this application is to advance the science of diagnostic error reduction. Diagnostic error (defined as the failure to provide the patient with an accurate and timely diagnosis or to communicate that explanation to the patient) is an important, common, and costly problem. These errors and their impact on patient outcomes, previously underemphasized, have been the subject of increasing attention secondary to the publication of the Institute of Medicine report Improving Diagnosis in Health Care, the AHRQ Research Summit on Improving Diagnosis in Health Care, and the formation of the Coalition to Improve Diagnosis by the Society to Improve Diagnosis in Medicine. Despite this tangible progress, the best means of identifying, measuring and preventing diagnostic errors remains unclear. Simply understanding the complex origins of diagnostic errors requires multidisciplinary involvement that includes the input of patients, clinicians, educators, human factors experts, and cognitive scientists, with support from other important stakeholders including payers and accrediting/credentialing organizations. Previous Conferences and Impact: Previous conferences, all supported by AHRQ, provided forums for groundbreaking research as well as a means of bringing together researchers and experts to focus on issues that lie at the intersection of diagnostic reasoning and medical error. They have resulted in the formation of research agendas and the identification of programs and initiatives that will lead to improvements in diagnostic safety. A key output of the prior conferences was the formation of the Society to Improve Diagnosis in Medicine, the sole national organization devoted to promoting diagnostic safety. Over the past several conferences, an emerging focus has been placed on identifying, promulgating and promoting specific strategies that have been demonstrated to improve diagnostic performance and safety. Conference Plan: The conferences will be 3.5-day meetings. As previously, the first day will center on summits designed to bring together key leaders in specific areas of the study of diagnostic error with research, patient and educational summits all planned. The subsequent conference will focus on practical means of improving diagnostic reliability through presentation of both research advances and practice innovations. There will be a concentration on the dissemination of interventions demonstrated to effect an improvement in diagnostic safety, with a specific focus being placed on the beneficial effect that improved teamwork can have on the diagnostic process. Specific emphasis will also be placed on promoting and encouraging research in the field. Speakers will be internationally recognized leaders from diverse disciplines including organizational development and teamwork, patient safety, patient engagement, and medical education. Impact/ Deliverables: The conferences will provide an opportunity to promote the development and dissemination of initiatives and strategies designed to reduce diagnostic errors and their impact on patients.